DESCRIPTION (Investigator's Abstract): The production of vasopressin and oxytocin by magnocellular neurons subserves homeostatic and reproductive functions which are critical to the survival of the individual as well as the species. As a result, these neurons are specialized for the production and storage of large quantities of hormone. Therefore, experiments are proposed to examine the mechanisms that couple hormone synthesis to hormone release. The following hypothesis will be addressed: 1- Under certain conditions, VP mRNA can be a determinant of VP release. This hypothesis will be addressed by examining the effect of manipulating VPmRNA content and translation with exogenous sense and antisense VPmRNA. Dispersed hypothalamic cultures will be used in these experiments. 2- The regulation of VP mRNA content in hypothalamic magnocellular neurons by cyclic AMP(cAMP) involves regulation of both VPmRNA transcription and turnover. Gene transcription will be evaluated in cultures of dispersed fetal hypothalamic neurons by monitoring the expression of intronic VPmRNA using in situ hybridization. The contribution of alterations in VP mRNA turnover will be assessed by evaluating the effect of actinomycin and cycloheximide on VPmRNA content of explants of the hypothalamo-neurohypophyseal system (HNS). Intracellular cAMP will be elevated either directly with 8-bromo-cAMP or indirectly through activation of adenyl cyclase with forskolin or by receptor mediated activation of adenyl cyclase with a D1 dopamine receptor agonist. 3- The intracellular signaling pathways involved in the regulation of OT gene expression are fundamentally different from those involved in regulating VP gene expression. Dispersed hypothalamic cultures will be used to identify the mechanisms responsible for OT expression by fetal neurons. Since numerous neuronal systems utilize peptides as chemical signals, elucidation of the mechanisms coupling synthesis and release of neuropeptides has broad application to the nervous system. Abnormalities in these coupling processes may underlie neuropathological conditions associated with the neurohypophyseal system as well as other neuronal systems. Therefore, the proposed studies will provide important insight into normal and pathological processes in the nervous system.